This invention relates generally to an ink droplet recording device and more particularly to such devices in which the droplets of marking fluid are selectively produced only when a mark is to be formed.
Ink drop printers which produce the droplets of marking fluid only as required for recording, known as drop-on-demand recorders, usually provide a print head, having a plurality of nozzles, which traverses a print line of the recording medium and is supplied with ink from a reservoir that is replenished as required. Examples are seen in U.S. Pat. Nos. 4,095,237 and 4,126,868.
Ink replenishment is frequently an inconvenience. Care must be taken to avoid the entrapment of air in the supply lines to the nozzles which would disable the nozzles, and care must be exercised to avoid spillage of a relatively messy liquid. The replenishment containers of ink are often complex in that they require the inclusion of a blotter and pierceable opening through which the ink is supplied to the printhead structure. The usual drop-on-demand printer also requires occasional cleaning which necessitates the removal of the nozzle and pump structure or the substitution of a cleaning liquid for the ink. On occasion, a nozzle becomes clogged so badly that it must be replaced. This may require replacement of the entire printing head.
The known recorders lack the facility for changing the nozzle size, and hence the drop size of the marking liquid. It is frequently desirable to change to fine printing quality by altering the pel or print element density. A further limitation is that of color. When one or more additional colors are to be used, there is usually a duplication of the nozzle structure and ink supply means for the particular color. This adds significant complexity and cost to the marking device.